OBJECTIVES: Polypharmacy, commonly defined as the ongoing use of 5 or more medicines by one person, is currently a major challenge in pharmacotherapy. A big challenge for the pharmaceutical care is to ensure the rational use of medicines. Drug interactions are a major threat to pharmacotherapy. The pharmacists have an irreplaceable role in reducing them. METHODS: A polypharmacy assessment was completed by a pharmacist and included a review of all drug therapies for 6 months in 100 patients (october 2016 - march 2017). All drug prescription, except for OTC drugs and food supplements, has been assessed. Drug interactions were analyzed according to the Lexicomp® database and the Summary of Product Characteristics (SmPC), drug duplication was also monitored. RESULTS: Pharmacotherapy reviewing by 100 patients (22-90 years old, median=68, average=67.73) we identified together 1 676 drug interactions (median=17, average=16.75). There were identified X type interaction (avoid combination) was present in 41% patients (3.99% share of all interactions, average=0.67); D type (consider therapy modification) was present in 92% patients (19.33% share of all interactions, average=3.24); C type (monitor therapy) was present in 100% patients (76.67% share of all interactions, average=12.85). The most common drug occurrence in X type interaction was ipratropium bromide (37.31% X type interaction). CONCLUSIONS: The results demonstrate the correlation of drug interactions with the polypharmacy. The pharmacists play a very important role in ensuring optimal pharmacotherapy of patients and they can contribute to increasing the safety of pharmacotherapy. But, the opportunities of pharmacists in health system in Slovakia is not sufficiently utilized.